Field of the Invention
The invention relates to a device for cross cutting material webs, in particular printed material webs after they have been printed in a rotary printing press.
The published German Patent Document DE 39 34 673 A1 concerns a cross cutting device for moving webs, wherein format length is adjustable. This is particularly suited for a folder disposed downline of a printing press. The cross cutting device is formed of two cylinders of like diameter arranged on opposite sides of the web, one of the cylinders, namely a knife cylinder, carrying at least one cutting knife borne by a cutting beam, and the other cylinder, namely an opposing or counter cylinder, carrying a corresponding number of flexible cutting bars, borne by bearing beams. To be able to cut different format lengths with a single pair of cylinders, the diameter of the knife cylinder is dimensioned so that, for the longest format, the circumferential cylinder speed is equal to or slightly greater (by about 3%) than the web speed, that furthermore each cutting beam and each bearing beam are mounted in the cylinders appertaining thereto so that they are swivellable about swivel axes parallel to the cylinder axes of rotation which lie within the axes of rotation, and that each cutting beam and each bearing beam is swivelled by a swivel mechanism during the cutting operation with adjustable travel (including zero travel for the longest format) periodically counter to the web running direction and subsequently back again into the starting position thereof, about the respective swivel axes thereof in the circumferential direction of the knife cylinder and the opposing cylinder, respectively.
The published European Patent Document EP 05 23 346 B1 concerns a device for transporting a paper web into a folder of a printing press. Applied to the cutting cylinders of a cutting-cylinder pair are material web-profiling strips, which superpose a profile reinforcing the web. The strips are adjoined by smoothening surfaces, which remove the web-reinforcing profile from the web again, the instant the leading end of the material web has entered the conveying device adjoining the pair of cutting cylinders. Smoothening surfaces and profiling strips are applied to the circumferential surfaces of the cylinders contacting the web, the cylinders themselves being formed as rotational bodies of solid material.
The Published Non-prosecuted Japanese Utility Model Application (JP Hei) 2 137 371 is concerned with a cutting device of a folder without puncture needles or pins. In a cutting device of a thus pinless folder, a folding roller having folding blades attached to the outer circumference thereof is freely rotatable. The knife-supporting roller is freely rotatable with respect to the folding roller. A narrow band of flexible material is arranged on the outer circumference of the folding roller and knife-supporting roller in the circumferential direction of the respective roller, alternating in the direction of the rotational axis of the respective rollers.
The published European Patent Document EP 0 523 435 B1 is concerned with a cross cutting device on folding units for web-fed rotary presses. This cross cutting device is formed of a cutting knife, which is rigid against bending and is arranged on a cutting cylinder, and a groove strip or reglet, which is arranged on a groove cylinder as an abutment for separating cut material. The groove reglet is formed of a unipartite groove member and a compression-spring member. Viewed in the direction of movement of the groove cylinder, initially the groove member and then the compression-spring member are arranged adjacent one another. The groove member of the groove reglet is formed of plastic material having low elasticity, whereas the compression spring member is formed of plastic material of higher elasticity compared with that of the groove member.
With regard to folders without pins or puncture needles, it has been known heretofore to cover the circumferential surfaces of the cutting cylinders with an elastic material, which may be adhesively bonded, for example, on the circumferential surfaces thereof. The elastic material has the effect of prestressing the material taken up during the cross cutting operation. The disadvantage of using such adhesively bonded elastic materials is that the surfaces thereof are worn out and abraded very quickly, and the downtime of a folder required for reconditioning the layers is very lengthy. The reconditioning of such elastic layers is also very time-consuming because it is usually very difficult to gain access to the cutting-cylinder pair in a folder.
In view of the hereinafore outlined disadvantages of the prior art, it is an object of the invention to provide a device for cross cutting material webs wherein the time period required for exchanging cylinder coverings is considerably reduced over the corresponding time period for the devices of the prior art, so that faster resumption of production can be ensured.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a device for cross cutting material webs, comprising a cutting-cylinder pair formed of mutually cooperating cylinders having respective cylinder cores and circumferential surfaces formed by exchangeable circumferential elements, the circumferential elements being arranged removably around the respective cylinder cores of the cylinders.
In accordance with another feature of the invention, the cylinder cores have lay surfaces and lay projections.
In accordance with a further feature of the invention, one of the cylinders is a knife cylinder, and the lay projections are arranged on the knife cylinder next to a knife mounting.
In accordance with an added feature of the invention, one of the cylinders is a groove cylinder, and the lay projections are arranged on the groove cylinder adjacent to a groove beam.
In accordance with an additional feature of the invention, the circumferential elements are formed of first circumferential elements and second circumferential elements, the first circumferential elements engaging around the second circumferential elements on the respective cylinder cores.
In accordance with yet another feature of the invention, the first and the second circumferential elements, respectively, are provided separately with a covering portion.
In accordance with yet a further feature of the invention, during assembly of the first and the second circumferential elements on the cylinder cores, respectively, a covering engageable over the first and the second circumferential elements, respectively, is clamped between the cylinder cores, respectively, and the first circumferential elements.
In accordance with yet an added feature of the invention, the first and the second circumferential elements are formed of elastically deformable material.
In accordance with yet an additional feature of the invention, the first and the second circumferential elements are formed of aluminum or an aluminum alloy.
In accordance with another aspect of the invention, there is provided a folder having a cutting-cylinder pair comprising a knife cylinder and a groove cylinder, having first and second circumferential surfaces, respectively, formed by exchangeable first and second circumferential elements arranged removably on the respective cylinder core of at least one of the knife cylinder and the groove cylinder.
In accordance with a concomitant feature of the invention, the folder is of the pinless type.
The advantages which this invention brings with it are of a diverse nature. The exchangeable circumferential elements can be removed simply and quickly from the cutting cylinder region on the folder, so that reconditioning of the covering does not have to be performed in the folder. Consequently, once the circumferential elements have been exchanged, the folder is again available for production. The worn-out circumferential surfaces of the exchangeable circumferential elements can be renewed again outside the folder, without therefore having to exchange the cutting-cylinder pair as a whole.
In a further refinement of the concept upon which the invention is based, the cylinder cores both of the knife cylinder and of the groove cylinder may be provided with lay surfaces and with lay projections in order to achieve easier centering of the circumferential elements. In this regard, the circumferential elements are arranged, in particular, symmetrically with respect to one another. The lay projections on the cylinders are arranged on the knife cylinder alongside the cutting knife mounting and are arranged on the groove cylinder alongside the groove beam. In an advantageous manner, the circumferential elements, which are received near the cutting knife mounting or near the groove beam, grasp the circumferential elements which are disposed opposite to the cutting tool mounting and opposite to the groove beam, respectively, at the ends thereof. In this manner, defined register surfaces and a smooth circumferential surface are attained on the cutting-cylinder pair.
The circumferential elements which are exchangeably fastened onto the cylinder cores may be both provided with portions of a covering, as well as, after mounting, wrapped in a continuous covering material. The ends of the continuous covering material may be clamped between the circumferential elements and the cylinder core and be subjected to tension in the circumferential direction.
The circumferential segments may either be produced entirely from an elastically deformable material or made from aluminum or an aluminum alloy.
The circumferential elements which are exchangeable according to the invention can be used both for cutting-cylinder pairs of folders, generally, or of folders which are pinless or without puncture needles.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for cross cutting material webs, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: